Work-Related Factors and Their Influence on Body Mass Index: A Retrospective Cohort Study in the French Tertiary Sector

<b>Background/Objectives:</b> Work environments play a crucial role in shaping lifestyle behaviors that influence body weight, yet the relationship between occupational factors and obesity remains underexplored. This study assessed the impact of work-related conditions on body mass index (BMI) trends in a large cohort of tertiary sector employees in France. <b>Methods</b>: A retrospective observational analysis was conducted using occupational health data from 23,853 employees in Paris. BMI changes were assessed through linear regression models, and associations between occupational exposures (e.g., night work, sedentary roles) and BMI variation were examined. <b>Results</b>: A total of 23,853 employees were analyzed. The mean age at first visit was 45.4 years (range 16-82), and 59% were women. Employees belonged to various socio-professional categories, with more than half in executive or intermediate positions. At baseline, 24% were overweight and 8.5% obese. Mean BMI was 23.5 kg/m² in women and 24.7 kg/m² in men, with average annual increases of 0.15 and 0.12 kg/m², respectively (<i>p</i> < 0.05). <b>Conclusions</b>: Work-related factors, particularly night shifts, sedentary roles, and lower occupational status, contribute to BMI increases among tertiary sector employees.